Co-doped Phosphate Glass Research Articles

Er3+/Yb3+ co-doped phosphate glass waveguides formed by the H+ ion implantation

The 400 keV proton implantation with a fluence of [Formula: see text] ions/cm2 was applied on the [Formula: see text] co-doped phosphate glass to fabricate a planar waveguide structure. The mode profile at the end face of the waveguide was measured by the end-face coupling technique. The energy loss profile of the energetic protons was calculated by the SRIM 2013. The refractive index distribution was simulated by the reflectivity calculation method. Based on these results, the formation theory of the planar waveguides was discussed through simulating the energy loss distribution and analyzing the reconstructed refractive index profile, which could be used for applications in the future integrated optical systems.

Concentration Effect of Germanium Dioxide on the Spectroscopic Properties and Laser Performance of Er3+/Yb3+ Co-Doped Phosphate Glasses

The Er3+/Yb3+ co-doped phosphate glasses with GeO2 modification (PGs) were successfully prepared by melt-quenching method. Their physical parameters were investigated such as density, refractive index, glass transition temperature and coefficients of thermal expansion. The phenomenological intensity parameters Ω t (t = 2, 4, 6) of the PGs have been calculated by the Judd-Ofelt theory. The relationship between optical properties and GeO2 concentration was discussed in this work. The laser experiment using PG10 (GeO2 10 mol% modified phosphate glass with Er3+/Yb3+ ratio of 0.5/2) was carried out. The research results indicate that the introduction of GeO2 results in a large absorption and emission cross-section, a long lifetime, a high quantum efficiency, and an excellent laser performance. All these advantages could also portend an optimized method for improving spectroscopic properties in other constituent Er3+/Yb3+ co-doped phosphate glass by introducing GeO2.

Mid-Infrared, Green and Red Emission in Ho3+ - Er3+ Co-Doped Phosphate Glasses

Over the past decades, phosphate glasses show ample advantages in laser technology because of their excellent optical properties like a low glass transition temperature, low phonon energy, large infrared transmission window, and high gain density. The inclusion of lead and alkali earth metals to these phosphate glasses also improves the chemical durability of glasses, which have more advantages in smart cards, medical applications, and micro-batteries. The optimum environment for chemical durability and incorporating rare earth ions can be achieved by the interaction between sulphate and phosphate ions. Moreover, phosphate glasses mixed with alkali sulphate provides scope for micro battery applications. The presence of network modifiers like Pb2+, Zn2+ in phosphate glasses introduces structural modifications and increases the number of non-bridging oxygens (NBOs) in glass network. The metal oxides like PbO, Bi2O3 makes phosphate glass suitable for rare earth ion incorporation by softening the glass and provides better distribution by controlling the formation of clusters. The wide variety of rare earth ions in the phosphate glasses leads to wide range of applications in optoelectronic devices.To overcome the difficulty associated with lack of a useful absorption band at 980 nm of Ho3+ ion (easy excitation by commercial laser diode (LD)), rare earth ions such as Tm3+, Yb3+, and Er3+ can be introduced. Especially, among them, Er3+ exhibit strong absorption at 980 nm. Due to the narrower energy gap between Er3+: 4I13/2 and Ho3+: 5I7 states, the emission of Ho3+ ions can be enhanced by addition of Er3+. So, the Er3+/Ho3+ co-doped glasses have promising applications in mid-infrared (MIR) laser applications with 980 nm LD. In view of this, the set of the Er3+/Ho3+ co-doped sodium-sulfo lead phosphate glasses was prepared with the molar composition of (20-x-y) Na2SO4-20PbO-60P2O5-xEr2O3-yHo2O3 (x=0.5, y= 0.2, 0.4, 0.6, 0.8, 1.0 mol %) named as GEH-y glass and coded as GExHy. To explore various possible applications, all prepared glasses are characterised by EDS, XRD, FTIR, absorption, photoluminescence and lifetime profiles. All results are computed and few of them are compared with other glasses.We present results focused on both mid infrared and visible emission properties of Er3+/Ho3+ions in sodium-sulfo lead phosphate (GExHy) glasses. These materials exhibit simultaneously DC (down-conversion) and UC (up-conversion) photoluminescence (PL) by excitation at 379 nm and 980 nm. The favourable concentration of Ho2O3 was estimated from the analysis of NIR PL spectra for Ho3+: 2.0 mm and Er3+: 1.5 mm. In GExHy glasses, the increase in intensity near 2.0 mm with decrease in intensity at 1.5 mm infers to energy transfer process between Er3+ and Ho3+ ions.Under lexc= 379 nm the Er3+ ions are pumped to the 4G11/2 excited state and depopulate {via multi phonon relaxation MPR1} at lower 4S3/2, 2H11/2, and 4F9/2 levels and then relaxed to the 4I15/2 ground state by emitting weak and strong green emission bands along with weak red emission related to 4S3/2→4I15/2 (522 nm), 2H11/2→4I15/2 (544 nm), and 4F9/2→4I15/2 (657 nm) transitions, respectively. The up-conversion energy transfer (ET) analysis with 980 nm LD excitation, undergoes the following mechanism: Ground state absorption (GSA) : Er: 4I15/2 + hν → Er: 4I11/2 Excited State Absorption (ESA1) : Er: 4I11/2+ hν → Er: 4F7/2 Excited State Absorption (ESA2) : Er: 4I13/2 +hν → Er: 4F9/2 CR1 (Cross Relaxation) : Er: 4I11/2+Ho: 5I6→ Er: 4I15/2+Ho: 5F4 CR2 (Cross Relaxation) : Er: 4I13/2+Ho: 5I6→ Er: 4I15/2+Ho: 5F5 ET1: Er: 2S3/2+Ho: 5I8→ Er: 4I15/2+Ho: 5S2+5F4 ⇒ Ho: 5S2+5F4 → 5I8 (545 nm) ET2 : Er: 4F9/2+Ho: 5I8→ Er: 4I15/2+Ho: 5F5 ⇒ Ho: 5F5→5I8 (659 nm) MPR2: Ho: 5S2+5F4 → 5F5 ET3: Er: 4I11/2+Ho: 5I8→ Er: 4I15/2+Ho: 5I6 ⇒ Er: 4I13/2 → 4I15/2 (1554 nm) ET4: Er: 4I13/2+Ho: 5I8→ Er:4I15/2+Ho Fig. 1 Schematic energy level diagram of GE0.5H0.8 glass.The maximum energy transfer efficiency of GExHy samples is 75.5% and with the increase of Ho3+ ions, the lifetime decay has been reduced from 5.06 ms to 1.24 ms. The absorption and stimulated emission cross-sections of Er3+:1.5 mm and Ho3+: 2.0 mm were calculated. Moreover, the FWHM × σemi was estimated for Ho3+:5I7→5I8 transition to estimate the probable MIR laser emission. The CIE color coordinates were estimated from both DC and UC PL spectra. All the results indicated that the prepared GExHy glasses have promising material applications in mid-infrared solid-state lasers and telecommunications. In addition, efficient green and red emission makes these glasses attractive for the phosphor applications. Figure 1

BiF3 Incorporation in Na/Ba Mixed Network Modifier Fluoride–Phosphate Glasses: Structural Studies by Solid-State NMR and Raman Spectroscopies

Bismuth-containing rare-earth codoped fluoride phosphate glasses are promising materials for superbroadband near-infrared (NIR) emission with potential applications in optical amplification. To elu...

Characterization of sub-nanosecond pulsed laser amplification with Er:Yb co-doped phosphate glass fibers

We present an experimental characterization of the amplification of sub-nanosecond duration laser pulses at a wavelength of 1538 nm in short custom-made Er:Yb phosphate glass fibers with different core diameters. The fibers vary in their diameter from 100 µm (highly multi-mode) down to 12 µm (single-mode). The peak power, energy per pulse, and spectral shape of the amplified signal are presented. With our input pulses, the measurements show that the large core diameter fibers do not increase the amplification of the 1538 nm signal. We believe this is due to the high re-absorption of the Er3+ ions in the phosphate fiber. The optimal fiber geometry was found to have a core diameter of 20 µm with a length of 14 cm. The maximum peak power is 8.25 kW, corresponding to a net gain of 10.9 dB, with a pulse duration of 0.7 ns and a repetition rate of 40 kHz.

Preparation and luminescent properties of Tm3+-Dy3+ co-doped phosphate glass for white light-emitting-diode applications

As a kind of rare earth luminescent material, the development of white light-emitting glass cannot be ignored. Here, we successfully prepared series of Tm3+-Dy3+ co-doped P2O5-SrO-BaO-ZnO glasses. Structural analysis showed that the glass network is mainly composed of orthophosphate, pyrophosphate, and metaphosphate units. In the case of a certain content of Tm3+ or Dy3+, the densities of PSBZ glasses increased with the increasing of Dy3+ or Tm3+ content. From the optical absorption spectra, eight distinctive absorption bands can be found in the wavelength of 300 nm–750 nm. Under the excitation of 354 nm UV light, four main peaks corresponded to the transition of 1D2 → 3F4 and 4F9/2 → 6HJ (J = 15/2, 13/2 and 11/2) were found at 452 nm, 483 nm, 574 nm, and 663 nm, respectively. Besides, the CIE chromaticity coordinates, CCTs, and fluorescence decay curves were recorded to confirm the glass Tm0.4Dy1.0 showed excellent chromaticity coordinates (0.3392, 0.3334), suitable CCT (5188K) and relatively high fluorescence lifetime (434.68 μs) compared to other glasses prepared in this work, indicating that this glass has potential applications in WLED devices.

Spectral characteristics and optical temperature sensing properties of Er3+/Yb3+-co-doped phosphate glasses with GeO2 modification.

Er3+/Yb3+-co-doped phosphate glasses with GeO2 modification (PLAZGs) were successfully prepared by the melt-quenching method. The phenomenological intensity parameters Ωt (t=2, 4, 6) of the PLAZGs have been calculated by the Judd-Ofelt theory. Based on the phenomenological intensity parameters, the spectroscopic parameters of Er3+ and fluorescence intensity ratio (FIR) of green upconversion emissions were estimated. It was observed that, under 980 nm excitation, all samples exhibit green and red upconversion emissions of Er3+. The 10 mol% GeO2 modified phosphate glass has the strongest upconversion emission. Additionally, the fluorescence decays of the 2F5/2→2F7/2 transition of Yb3+ ions were measured to evaluate the energy transfer efficiency from Yb3+ to Er3+ ions. Finally, the optical temperature sensing properties based on upconversion emissions were investigated at temperatures from 150 K to 600 K. The maximum absolute temperature sensitivity S value of 6.0×10-3K-1 at 400 K is obtained, which indicates that the glass is promising for temperature sensing application based on the FIR technology.

Concentration effect of Yb3+ ions on the spectroscopic properties of high-concentration Er3+/Yb3+ co-doped phosphate glasses

High-concentration erbium-ytterbium (Er3+/Yb3+) co-doped phosphate glasses were manufactured by the melt-quenching method. The phosphate glass matrix was 58.5P2O5–11K2CO3–11BaCO3–7Al2O3–2ZnO-0.5Er2O3-xYb2O3 (x = 10, 11, 12, and 13 mol%). Various spectroscopic parameters of glasses were measured as a function of the matrix composition, temperature control, dehydration and the Er3+/Yb3+ concentration to evaluate the potential of these glasses to act as a laser material for the eye-safe laser emission (1.53 μm). The density, refractive index, glass-transition temperature, and softening temperature increase gradually with the increase of Yb3+ concentration. The glass sample with 12 mol% Yb2O3 did not show devitrification even when the temperature reached 850 °C. The optimized Er3+/Yb3+ ratio of 0.5/12, gives the highest luminescence intensity at 1535 nm under 980 nm excitation. The luminescence lifetime for 4I13/2 of Er3+ ions is 7.85 ms. The emission cross section at 1535 nm was calculated to be 7.11 × 10−21 cm2 by using the McCumber theory.

In situ-monitored enhancement and quenching effect of Cu nanoclusters on Sm3+ photoluminescence in glass

An assessment of the influence of heat treatment temperature and retention time on the optical properties of a Cu+ and Sm3+ co-doped phosphate glass of interest to photonic applications is reported. Particularly, the enhancement of the orange-red photoluminescence (PL) from Sm3+ ions has been realized in the glass through the development of non-plasmonic Cu clusters. It was exposed during an in situ isothermal treatment wherein optical absorption and PL were monitored together in real time. Following the PL increase, a drop in the Sm3+ emission intensity was produced concurring with the appearance of Cu nanoparticles (NPs) exhibiting the surface plasmon resonance. Hence, the connection between energy donor (sensitizing) effects of small Cu clusters and the energy acceptor (quenching) character of Cu NPs is supported. It is the first time to the author's knowledge that the enhancement of Sm3+ luminescence via Cu clusters embedded in glass is indicated.

(INVITED) Impurities in large scale produced Nd-doped phosphate laser glasses. I. Cu ions

Impurity ions such as transition metals and rare earth metals in Nd-doped phosphate laser glasses will degrade Nd-laser performance, among which Cu is the most harmful. Divalent Cu2+ not only results in an optical loss at Nd-laser wavelength, but also reduces the energy storage for laser amplification. A large-scale production of Nd-doped phosphate laser glasses is required to meet quality demand and to realize economy of scale. To balance between the controlled impurity level in the glasses and the cost of raw materials for thousands of slabs of meter-scale Nd-doped phosphate laser glasses, it is important to determine an upper limit for Nd-laser degradation due to divalent Cu2+ ions. The absorption edge of Cu singly-doped phosphate glass prepared in an oxidizing atmosphere shows the evidence of monovalent Cu+. X-ray photoelectron spectroscopy is utilized to further verify the existence of monovalent Cu+ ions in Cu, Nd codoped phosphate glass. The results show that both Cu+ and Cu2+ ions most probably coexist in Nd-doped phosphate laser glasses produced in the oxidizing atmosphere to eliminate Pt inclusions in the glasses. Accordingly, this paper discusses the extinction coefficient and the fluorescence quench factor caused by divalent Cu2+ ions, as well as their influence.

Upconversion and 1.53 μm near-infrared luminescence study of the Er3+-Yb3+ co-doped novel phosphate glasses

Er3+-doped glasses are important materials to develop upconvertors, sensors, optical fibers and green solid state lasers. The upconversion and near-infrared transitions in Er3+-Yb3+ co-doped phosphate glasses are studied in this work and an improvement of 45% in the quantum efficiency of the glasses is observed by the addition of 1 mol% of Yb2O3. Judd-Ofelt analysis, lifetime of some excited states of Er3+ ions and energy transfer mechanisms are discussed.

Good optical performances of Eu3+/ Dy3+ / Ag nanoparticles co-doped phosphate glasses induced by plasmonic effects

Sodium zinc phosphate glasses containing silver nanoparticles (Ag NPs), Eu3+ and Dy3+ ions, have been prepared using the melt-quenching method. The structure, luminescence and spectroscopic properties were evaluated through experimental and theoretical studies. The results indicate that a dual mode energy transfer from Ag NPs and Dy3+ ions to Eu3+ ions leads to the enhancement of the emission bands related to Eu3+ ions in addition to the local field effect of the silver NPs. Moreover, the excited Dy3+ ions exchange energy with Eu3+ in the presence of Ag NPs and Ag nanoclusters (Ag NCs) produces white color with varying tints. The present systematic study provides useful information for the development of light emitting diodes (LEDs) devices.

Tunable luminescence and energy transfer properties based on La2O3-P2O5:Dy3+/Tm3+ glasses

The white-LED material Dy3+/Tm3+ co-doped phosphate glass was prepared by a conventional melting method. The energy transfer in the two rare earth ions was supposed by changing the concentration of one doping ion and was further demonstrated by the fluorescence lifetime. The energy level transition mechanism between the rare earth ions was analyzed using the Inokuti–Hirayama theory. There were two kinds of energy transfer mechanisms from the dipole–quadrupole interaction (Dy3+ → Tm3+) and the quadrupole–quadrupole interaction (Tm3+→Dy3+). The luminescence color was tuned from a blue to a near standard white light emission using 350 nm excitation and adjusting the rare earth ion doping ratio. The results show that 15La2O3-85P2O5:xDy2O3-yTm2O3 glass is a promising UV-excited white photodiode material.

The effect of silica additive on the structural and luminescence properties of Eu3+/Tb3+ co-doped metaphosphate glasses

In this paper, we investigate the effect of silica additive on the structural and luminescence properties of Eu3+ and Eu3+/Tb3+co-doped sodium-calcium phosphate glasses. Eu3+ doped phosphate glasses have been prepared using melt-quenching technique and characterized through X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier Transform Infrared (FTIR), Raman spectroscopy, ultraviolet–visible (UV–Vis) and luminescence measurements at room temperature. The incorporation of SiO2 led to an increase of glass transition temperature (Tg), indicating an improvement of glass network rigidity. This result was correlated with FTIR and Raman investigations which revealed the occurrence of more hydration-resistant POSi bonds. An intense red luminescence has been observed due to 5D0 → 7F2 transition of Eu3+ ions in these glasses. The luminescence spectra for Eu3+/Tb3+ co-doped phosphate glasses were then recorded with various Eu3+:Tb3+ molar ratio. Dependence of luminescence lifetimes on the increase of Eu3+: Tb3+ molar ratio was investigated. It was observed that the energy transfer process occurs from Tb3+ to Eu3+ in the studied glasses. Our results show that a tuneable color is achieved when Eu3+: Tb3+ molar ratio changed. The variation of the excitation wavelength can also tune the luminescence spectra of the new phosphate glasses.

Up-conversion luminescence and highly sensing characteristics of Er3+/Yb3+ co-doped borophosphate glass-ceramics

Er3+/Yb3+ co-doped phosphate glass ceramics (GC) with a cubic KAlSi2O6type structure were successfully fabricated by traditional melt-quenching technique and subsequent heat treatment. Structural characterization of the GC was achieved by X-ray powder diffractometer (XRD) combined with transmission electron microscope (TEM). The up-conversion (UC) optical properties were systemically investigated through absorption spectra, photoluminescence spectra, pump power dependent UC emission spectra, and UC decay curves. The possible energy transfer process and the transition channels were analyzed by using energy level diagram. Results show that the UC luminescence performance of the GC was enhanced compared to precursor glass (PG). Moreover, the temperature dependent UC emission spectra of the GC were measured in the temperature range of 298–798K under 980 nm laser excitation. Combined with the fluorescence intensity ratio (FIR) technique, the UC emissions of Er3+/Yb3+ co-doped GC with two thermally coupled energy levels (TCELs) of 525 nm (Er3+: 2H11∕2→4I15∕2) and 549 nm (Er3+: 4S3∕2→4I15∕2) were studied as a function of temperature in the range of 298–798K. For optimized Er3+/Yb3+ co-doped GC, the theoretical maximum value of relative sensitivity Sr−max is 1.67 % K−1 at 298 K, and absolute sensitivity Sa−max is 4.59 ×10−3 K−1 at 570 K, which indicates that the Er3+/Yb3+ co-doped phosphate GC is a very promising candidate for optical temperature sensors with higher sensitivity.

Effect of microstructure on up-conversion luminescent of Tb3+/Yb3+ co-doped phosphate glass and glass-ceramic

Tb3+/Yb3+ co-doped precursor glass was synthesized by melt quenching method, and transparent glass-ceramic was prepared by heat treatment the precursor glass. Comparing the X-ray diffraction patterns of precursor glass and glass-ceramic showed that the Na3.6Y1.8(PO4)3 crystals were formed after heat treatment. By the scanning electron microscopy images of glass-ceramic, the grainy crystal grains were observed dispersed in the glass matrix. The structure of precursor glass and glass-ceramic was studied by FTIR spectra and Raman spectra, indicating that phosphate group was formed in glass-ceramic. The up-conversion luminescent intensity of glass-ceramic was obviously enhanced than precursor glass. Moreover, the luminescence quantum yield of the glass-ceramic sample showed higher than precursor glass, which can be attributed to the formation of phosphate groups in glass-ceramic.

Sm3+ and Gd3+ Co-doped lead phosphate glasses for γ-rays shielding and sensing

Six samples of rare earth (Sm3+ and Gd3+) co-doped lead alumino phosphate glasses of composition (58.2–2 x)PbO-40P2O5 − 1.8Al2O3-xSm2O3-xGd2O3 (where x = 0.4, 0.6, 0.8, 1.0, 1.2 and 1.4 mol%) were synthesized and explored for its scintillation properties. Prepared samples are found to have high density and better radiation shielding properties than halide scintillator and some conventional concretes and alloys. Optical characterization of samples confirms strong sensitivity for absorbing UV–visible radiation and enhanced luminescent properties due to energy transfer/energy down conversion process from Pb2+ to Gd3+ and then to Sm3+. Prepared samples when stimulated with high energy radiations under proper design suggest their possible use as high energy radiation detection and phosphors in scintillation counters for gamma-rays and X-rays detection. The synthesized glass systems are promising materials for developing optoelectronic devices like lasers and optical amplifiers, and gamma rays shielding material for radioactive waste encapsulation and detection of radiations.

Temperature Dependent Spectroscopic Properties of Cu+ and Dy3+ Co-Doped Phosphate Glass: Band Gap Analysis and Cu Nanocluster-Enhanced Dy3+ Luminescence.

This paper reports on the effects of temperature on light absorption and emission in Cu+ and Dy3+ co-doped phosphate glass, which is of interest for photonic applications. First, the temperature dependence of the absorption edge of the glass in connection with Cu+ ions absorption was assessed. A thermally-induced red shift attributed to Cu+ ion-lattice interactions was observed and analyzed through optical band gap determinations in the context of indirect-allowed transitions. Application of the Varshni model for the dependence of the energy gaps with temperature allowed to estimate the 0 K energy gap at 2.87 (±0.01) eV. Furthermore, Dy3+ photoluminescence (PL) along with Cu nanoparticles (NPs) absorption was monitored in real-time during an isothermal treatment by the in situ concurrent PL and absorption microspectroscopy technique. Periods of enhancement and quenching of Dy3+ emission linked to bidirectional energy transfer processes involving non-plasmonic Cu clusters and plasmonic Cu NPs were revealed. The formation of Cu NPs was promoted by tin(II) used as reductant. It is the first time to the author's knowledge that the 0 K energy gap is estimated for a highly Cu+ -doped glass and that the enhancement of Dy3+ PL by Cu clusters is exposed.

Energy transfer studies and neutral to warm white light generation in Dy3+-Sm3+ co-doped bismuth phosphate glasses for lighting applications

A series of bismuth phosphate (BiP) glasses activated with 0.5 mol% of Dy3+ and different concentrations (0.1, 0.3, 0.5, 1.0, 1.5 and 2.0 mol%) of Sm3+ ions were prepared by melt quenching technique. These are characterized through optical absorption, photoluminescence and decay measurements for spectroscopic investigations. The luminescence spectra have been studied under selected excitation wavelengths to examine the energy transfer mechanism in the present Dy3+-Sm3+ co-doped glass by varying Sm3+ ion concentration. The lifetimes of both 4F9/2 level of Dy3+ ion and 4G5/2 level of Sm3+ ion of co-doped glasses have obtained and found to be decreased with increase in Sm3+ ion concentration. The emission intensity increased with the increase of Sm3+ ion concentration (upto 1.5 mol%) which confirms the energy transfer process between Dy3+ to Sm3+ ions. The CIE chromaticity co-ordinates (x, y), correlated color temperature (CCT) and color purity (CP) were determined from the emission data. From the CIE, CCT and CP values, it can be concluded that there is a color hue from neutral to warm white light region due to Sm3+ ion concentration and selected excitation wavelength. Hence, the obtained results strongly suggest that the present Dy3+-Sm3+ co-doped bismuth phosphate glasses could be useful for lighting applications.

Sensitized deep-UV excitation of Tm3+ ions in strontium phosphate glasses with Sb3+ co-doping

The novel Tm3+/Sb3+ co-doped phosphate glasses are studied in response to an improvement of blue light emitting source. The analysis of J-O intensity parameters suggests that the present strontium phosphate glass is an appropriate matrix for Tm3+ doping to obtain an enhanced blue emission. The 5 s2-type Sb3+ ion serves as a sensitizer to transfer its strong allowed excitation in the deep UV region to Tm3+ effectively. PL and PLE spectra show that by Sb3+ co-doping, the blue emission of the Tm3+ doped strontium phosphate glass is enhanced greatly, while the excitation band of Tm3+ extends largely to the deep UV region. The emission decay curves of Sb3+ demonstrate the existence of the energy transfer (ET) process from Sb3+ to Tm3+ with the maximum efficiency and probability of ET as 20.43% and 9.20%, respectively. The emission color of these glasses can be adjusted from warm to cold blue via modulating excitation wavelengths. The present work suggests that Sb3+/Tm3+co-doped strontium phosphate glasses are promising for applications in blue emitters and plasma display panels.